A JISC-funded initiative has produced a set of books based on Open Access materials:

http://www.jisc.ac.uk/whatwedo/programmes/digitisation/econtent11/l... .

I think this is a great step forward, and it seems that there is also an option to update those books - pretty similar to the idea of Evolving Review Articles, as currently up for crowdfunding at 

http://rockethub.com/projects/3755-transforming-the-way-we-publish-.... However, while the former employs a complex mix of licenses, the latter is exclusively focused on openly licensed materials (see accompanying perspective).